Date: 1801
From: Rabbi Moshe Sofer
To: Unknown recipient
The questioner asks whether selling a horse to a non-Jew should be forbidden according to those who hold techumin are biblical. The Chasam Sofer dismisses this based on the Ran's distinction and argues that biblical techumin derive from the manna narrative, not from the melacha framework.
Source: Shu"t Chasam Sofer OC §152